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THE HUMAN GENOME
From Peas and fruit flies to humans…
What is a genome???
All the genetic information (genes) that make up an organism
What makes us human? Analyze human chromosome… Karotype
Picture of all the chromosomes in an organism
Autosomes○ CHROMOSOMES 1-44 (pairs 1-
22)○ Autosomal chromsomes
Sex chromosomes○ Determine a person’s sex (male
XY or female XX)○ Chromosome 45 and 46 (set 23)
DNA
DNA Structure Deoxyribonucleic Acid DNA is a polymer made
up of many monomers called nucleotides
Nucleotide contains: 5-carbon sugar called
deoxyribose RNA contains
RIBOSE sugar instead
Phosphate group One Nitrogenous
base (there are 4 types)
What are these Nitrogenous bases???
Make up the “steps” of the DNA ladder One Step= A Purine + A
Pyrimidine Purines
Double ring structure Adenine Guanine
Pyrimidines Single-ring structure Cytosine Thymine (in DNA only) Uracil (in RNA only)
Nucleic Acids DNA
Double strandDeoxyribose sugarA=TG=C
RNASingle StrandRibose sugarA=UG=CUracil is the
nitrogenous base used instead of THYMINE
DNA Review
The 2 Fates of DNA
DNA Replication(if cell enters cell
division…S-phase)
Protein Synthesis(when cell is doing is normal job-in G1 phase of cell cycle)
DNA Facts All living things have DNA
Prokaryotes-DNA in cytoplasm, simple○ Contain extra DNA called
PLASMIDSEukaryotes-DNA in nucleus,
complex DNA codes for the same 20 amino
acids in ALL living thingsIt is the UNIVERSAL code...all
organisms have the same A,T,G and C bases and the same 20 a.a., just arranged differently
The DNA backbone Putting the DNA
backbone togetherrefer to the 3 and 5 ends
of the DNA○ the last trailing carbon
OH
O
3
PO4
base
CH2
O
base
OPO
C
O–O
CH2
1
2
4
5
1
2
3
3
4
5
5
Sounds trivial, but…this will beIMPORTANT!!
Anti-parallel strands
Nucleotides in DNA backbone are bonded from phosphate to sugar between 3 & 5 carbonsDNA molecule has
“direction”complementary strand runs
in opposite direction
3
5
5
3
Bonding in DNA
….strong or weak bonds?How do the bonds fit the mechanism for copying DNA?
3
5
3
5
hydrogenbonds
Base pairing in DNA Purines
adenine (A)guanine (G)
Pyrimidinesthymine (T)cytosine (C)
PairingA : T
○ 2 bondsC : G
○ 3 bonds
Copying DNA Replication of DNA
base pairing allows each strand to serve as a template for a new strand
new strand is 1/2 parent template & 1/2 new DNA○ semi-conservative
copy process
DNA Replication Large team of enzymes coordinates replication
Let’s meetthe team…
Important Enzymes DNA Helicase
Unzips original DNA strand
DNA PolymeraseAdds nucleotides to the
unzipped sides DNA Ligase
Attaches/glues DNA fragments together on one of the new copies
How does DNA replicate itself?
Template mechanism What is a template??? Like the negative of a photograph
DNA Replication Process of copying the DNA molecule
○ What phase of the CELL CYCLE?S-phase….
2 strands of double helix separate (Unzips)
Each strand acts as a negative for making the new complementary strand
Nucleotides line up one by one following base pairing rules
Enzymes (DNA Polymerase and DNA Ligase) link nucleotides together to form 2 new DNA strands called the daughter strands
Fate #2: Protein Synthesis You already know about this…central
dogma of Biology Just need to know your key players…
The Protein Synthesis Team DNA mRNA tRNA rRNA Codons Anticodons Amino acids Proteins Introns Exons
Central Dogma of Biology
DNAmRNAprotein DNA TRANSCRIBES
to mRNAProcess is called
transcription mRNA TRANSLATES
to proteinsProcess is called
translationmRNA actually makes
amino acids, which come together to make proteins
DNAmRNAamino acids/polypeptide chain (Proteins)
DNA codes for an RNA strand The every 3 bases on the RNA
strand code for a specific amino acidCODON: three sequential
bases that code for a specific a.a. (20 a.a. total)
Amino acid are strung together to make a protein (primary structure)
Change DNA will change RNA which will change amino acids, which change protein
DNAmRNAProtein Transcription
Different form of the same message
DNA makes single stranded RNA (U replaces T)
RNA leaves nucleus Translation
Translate from nucleic acid language to amino acid language
Uses codons, 3-base “word” that codes for specific a.a.○ “code” for an amino
acidSeveral codons make a
“sentence” that translates to a polypeptide (protein)
Start Codons
UAA UGA UAG
Stop Codons
AUG
Three Types of RNA mRNA tRNA rRNA
Three Types of RNA… #1 mRNA (messanger RNA)
RNA transcribed from DNA templateModified in nucleus before if exits
○ RNA splicing: process in which Introns are removed and exons re joined together to make a continuous coding mRNA molecule
Introns○ Internal non-coding regions of DNA and mRNA○ Space fillers/jibberish○ They are cut out of mRNA before it is allowed to
leave the nucleus○ Process is called RNA splicing (processing)
Exons (MOST important part of DNA)○ Coding region of DNA and mRNA that will be
translated (Expressed)○ VERY important part of mRNA…it is carrying the
message from DNA (def can’t cut this out)
Three Types of RNA…#2 tRNA (transfer
RNA)The interpreterTranslate 3-letter
base codes into amino acids
Carries anti-codon on one end (three letters opposite of what is on mRNA)
Carries amino acid on other end
Anti-codon recognizes codon and attaches
Three Types of RNA…#3 rRNA (ribosomal
RNA)Found in ribosomeRibosome composed of 2
subunits:○ Small subunit for mRNA to
attach○ Large Subunit for two
tRNAs to attach“P” site: holds the tRNA
carrying the growing polypeptide chain
“A” site: holds the tRNA that is carrying the next a.a. to be added to the chain
When stop codon (UAA, UAG, UGA) is reached, translation ends and polypeptide is released
MUTATIONS
Mutations
Occur when there is an error in DNA replication
Def: Change in genetic material Mutagens
Physical or chemical agents that cause mutations○ Ex: high energy radiation (x-ray or UV)○ Ex. Chemicals (that are similar to DNA but
cause incorrect base pairing)
MutationAny change in the nucleotide sequence of
DNALarge or small
2 Main typesPoint Mutation
○ Base SubstitutionsFrameshift MutationInsertions or deletions
Base Substitution Replacement of one base or nucleotide with
another Usually do not change amino acid Sometimes causes a change in the protein made Silent Mutation
When a substitution does not cause a change in the protein expressed by a gene
Remember some codons represent the same amino acid
Example: GAA and GAG both code for Glu
Point MutationA point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence, such as this example, where we change the 'c' in cat to an 'h':
Original: The fat cat ate the wee rat. Point Mutation: The fat hat ate the wee rat.
Insertion or Deletion Nucleotide is removed or added More disastrous mRNA is read as triplet codes
Adding/removing bases changes these three letter codes
Codons downstream from insertion/deletion will be regrouped and probably code for a non-working protein
Result: FRAMESHIFT MUTATIONShift the “reading” frame of the genetic message
Frameshift mutation Original: The fat cat ate the wee rat. Frame Shift: The fat caa tet hew eer at.
Chromosomal Mutations
Involve changes in the number or structure of the chromosome
Chromosomal Disorders
Mechanics of meiosis (where we separate chromosomes) is usually pretty good
But nobody’s perfect…mistakes happen…. Most common problem…
Nondisjunction: when homologous chromosomes fail to separate properly
Literally means “not coming apart”If this occurs, ABNORMAL #s of chromosomes
may find their way into gametes and a disorder of chromosome number may result
Nondisjunction If one of the gametes with an ABNORMAL #
ends up getting fertilized, MAJOR problems!!!Trisomy: “three bodies”
○ Occurs when an autosomal chromosome fails to separate during meiosisWhen do chrm separate?
- Anaphase I and Anaphase 2
○ One gamete ends up with an extra copy of a chromosome and then the fertilized zygote ends up with 3 copies of a chrm instead of 2
○ Example: Downs Syndrome
Chromosomal Mutations May change location of
genes on chromosome Include:
Deletions: loss of part of chromosome
Duplications: produce extra copies of parts of chromosome
Inversions: reverse direction of chromosome
Translocation: when one chromosome breaks off and attaches to another
Mutations NOT always harmful Some alter a protein in a beneficial
way that may help species in a specific environment
If mutation is present in organisms gametes, it may be passed off to off-spring
Mutations are the ULTIMATE source for GENETIC DIVERSITY!!!
What is biotechnology? Here are some hints…
Biotechnology
Manipulation of living organisms or their parts to produce useful products
Main use is to improve human health and food production Seedless fruitsMake insulin
Genetic engineering
The transfer of genes or pieces of DNA from one organism into another organismNew DNA is a combination of pieces from
two different organisms…called recombinant DNA
Used to introduce new characteristics into organisms and populations
Gentically Modified Organisms GMOs
How to make recombinant DNA Use DNA from complex organism (human) and
transfer to a simple organism (bacteria) Uses a PLASMID
Small circular DNA in bacteriaIt is called a VECTOR when used in genetic
engineering
Genetic Engineering Positive/benefits
Make medicine like insulin and vaccines plentiful and inexpensive
Improves crop plants like corn and rice○ Grow faster and
stronger○ Resist disease and
insects○ Genes can be added
to add more vitamins to plants
Negatives/ConsUnknown long term
effects if ingested by humans
Harm native, natural species
Cross pollination between GMOs and wild plants resulting in unwanted hybrids (mockingjays!)
***Decreases genetic variation
DNA Fingerprinting
Not like the fingerprint on your hand
Used to determine the paternity of a child and in forensics (the CSI stuff you see on TV)
The chemical structure of everyone's DNA is the same. Only difference is order of base pairs Too many bases to analyze every
single one, so scientists analyze groups /segments of bases
These patterns do not, however, give an individual "fingerprint," but they are able to determine: If samples are from the same person,
related people, or non-related people. There are a few small fragments in
humans that scientists KNOW vary greatly from individual to individual
They analyze those segments and get a certain probability of a match
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